Fuel vapor recirculation tubes are used in motor vehicle fuel tank filler tubes to recirculate fuel vapor during refueling from a nozzle inserted in the filler tube with a mechanical seal provided about the nozzle. The recirculated vapor provides a make-up flow below the nozzle seal to prevent the flow discharging from the nozzle from creating a vacuum in the filler tube and prematurely activating the automatic nozzle shutoff.
Known fuel tank filler tube installations having a vapor recirculation tube attached to a port in the filler tube below the nozzle seal. This configuration sometimes allows liquid fuel to enter the vapor recirculation tube and flow into the vapor vent system when liquid fuel rises in the filler tube as the tank is filled. Liquid fuel in the vapor vent system can block the vapor vent lines, trap fuel in low regions of the system or even cause degradation of the vapor storage medium in the vapor storage canister if fuel enters the canister.
Known filler tubes also have a tapered nozzle chamber in the vicinity of the recirculation tube. The nozzle chamber surrounds the end of the nozzle when it is inserted into the filler tube and helps generate a vacuum condition in when mechanical seals are used. The diameter of the nozzle chamber around the nozzle should allow enough liquid to flow between the inner diameter of the nozzle chamber and the outer diameter of the nozzle to avoid excess fuel tank pressure when the nozzle fails to shut off. However, the length of the nozzle can vary, causing the ends of different nozzles to reach different areas in the nozzle chamber. Because the vacuum created in the filler tube depends on how much space is between the tip of the nozzle and the surrounding filler tube, filler tubes with a tapered nozzle chamber will generate inconsistent vacuum conditions because different nozzle lengths will end at different diameter portions of the nozzle chamber.
There is a desire for a way to protect a fuel vapor recirculation system from liquid fuel flowing into the vapor lines and to do so in a manner that is simple and low in cost and does not require substantial reworking or retooling of the fuel tank filler tube. There is also a desire for a reliable way to generate a consistent vacuum in the nozzle chamber regardless of the nozzle length.